Diamond uses/applications based on single-crystal CVD diamond produced at rapid growth rate

ABSTRACT

The present invention is directed to new uses and applications for colorless, single-crystal diamonds produced at a rapid growth rate. The present invention is also directed to methods for producing single crystal diamonds of varying color at a rapid growth rate and new uses and applications for such single-crystal, colored diamonds.

This application is a continuation of U.S. application Ser. No.11/599,36, filed Nov. 15, 2006, and claims priority benefit of U.S.Provisional Application No. 60/72,584, filed on Nov. 15, 2005.

STATEMENT OF GOVERNMENT INTEREST

This invention was made with Government support under Grant No.EAR-0421020 awarded by the National Science Foundation. The Governmenthas certain rights in this invention.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable.

SEQUENCE LISTING

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to uses and applications for diamond. Moreparticularly, the present invention relates to applications and uses ofsingle-crystal diamond produced at a high growth rate using MicrowavePlasma Chemical Vapor Deposition (MPCVD) within a deposition chamber.

2. Description of Related Art

Large-scale production of synthetic diamond has long been an objectiveof both research and industry. Diamond, in addition to its gemproperties, is the hardest known material, has the highest known thermalconductivity, and is transparent to a wide variety of electromagneticradiation. Monocrystalline diamond in particular possess a wide range ofimportant properties, including a low coefficient of thermal expansion,the highest known thermal conductivity, chemical inertness, wearresistance, low friction, and optical transparency from the ultra-violet(UV) to the far infrared (IR). Therefore, it is valuable because of itswide range of applications in a number of industries and researchapplications, in addition to its value as a gemstone.

For at least the last twenty years, a process of producing smallquantities of diamond by chemical vapor deposition (CVD) has beenavailable. As reported by B. V. Spitsyn et al. in “Vapor Growth ofDiamond on Diamond and Other Surfaces,” Journal of Crystal Growth, vol.52, pp. 219-226, the process involves CVD of diamond on a substrate byusing a combination of methane, or another simple hydrocarbon gas, andhydrogen gas at reduced pressures and temperatures of 800-1200° C. Theinclusion of hydrogen gas prevents the formation of graphite as thediamond nucleates and grows. Growth rates of up to 1 μm/hour have beenreported with this technique.

Subsequent work, for example, that of Kamo et al. as reported in“Diamond Synthesis from Gas Phase in Microwave Plasma,” Journal ofCrystal Growth, vol. 62, pp. 642-644, demonstrated the use of MicrowavePlasma Chemical Vapor Deposition (MPCVD) to produce diamond at pressuresof 1-8 kPa at temperatures of 800-1000° C. with microwave power of300-700 W at a frequency of 2.45 GHz. A concentration of 1-3% methanegas was used in the process of Kamo et al. Maximum growth rates of 3μm/hour have been reported using this MPCVD process. In theabove-described processes, and in a number of other reported processes,the growth rates are limited to only a few micrometers per hour.

Methods of improving the growth rates of single-crystal chemical vapordeposition (SC-CVD) diamonds have recently been reported [1, 2, 3, 4,5]. SC-CVD diamonds reported so far, however, are relatively small, arediscolored, and/or are flawed. Large (e.g., over three carats, ascommercially available high pressure, high temperature (HPHT) syntheticIb yellow diamond), colorless, flawless synthetic diamonds remain achallenge due to slow growth and other technical difficulties [7, 8, 9].The color of SC-CVD diamonds in the absence of HPHT annealing can rangefrom light brown to dark brown, thus limiting their applicability asgems, in optics, in scientific research, and in diamond-basedelectronics [6, 7, 8]. SC-CVD diamonds have been characterized as typeIIa, i.e., possessing less than 10 ppm nitrogen, and have coloration andother optical properties arising from various defects and/or impurities.

A diamond crystal of 10 carats is approximately five times that ofcommercially available HPHT diamond and the SC-CVD diamond reported inReferences [7, 8, 9, 10]. Single-crystal diamonds with larger mass(greater than 100 carats) are needed as anvils for high-pressureresearch, and crystals with large lateral dimensions (greater than 2.5cm) are required for applications such as laser windows and substratesfor diamond-based electronic devices. High optical quality(UV-visible-IR transmission) and chemical purity are required for all ofthe above applications. The large SC-CVD diamonds produced so farpresent problems because of the brownish color.

Attempts have been made to add oxygen in the growth of polycrystallineCVD diamond. These effects include extending the region of diamondformation [12], reducing silicon and hydrogen impurity levels [13],preferentially etching the non-diamond carbon [11, 14], and attemptingto prevent diamond cracks due to an absence of impurities [13]. Theseattempts were directed primarily to the etching and synthesis ofpolycrystalline diamonds but not to the production of SC-CVD diamond.

Attempts have also been made to intentionally vary the color of thesingle-crystal diamond formed. Yellow diamonds, for instance, have beenproduced that are similar to HPHT synthetic Ia or Ib diamond inappearance [6].

U.S. Pat. No. 6,858,078 to Hemley et al. is directed to an apparatus andmethod for diamond production. The disclosed apparatus and method canlead to the production of diamonds with a light brown color.

U.S. Provisional Application No. 60/684,168, filed May 25, 2005, whichis hereby incorporated in its entirety by reference, is directed toproducing colorless, single-crystal diamonds at rapid growth rate usingMicrowave Plasma Chemical Vapor Deposition (MPCVD) within a depositionchamber.

Until now, few attempts have been made to develop products which usesingle-crystal diamonds produced by MPCVD. Moreover, few attempts havebeen made to develop uses and applications for single-crystal diamondsthat are not doped with impurities.

Thus, there remains a need to develop new uses and applications forcolorless, single-crystal diamonds produced at a rapid growth rate.There also remains a need to develop new uses and applications forsingle-crystal diamonds of varying color grown at a rapid growth rate.

SUMMARY

Accordingly, the present invention is directed to new uses andapplications for colorless, single-crystal diamonds produced at a rapidgrowth rate. The present invention is also directed to methods forproducing single crystal diamonds of varying color at a rapid growthrate and new uses and applications for such single-crystal, coloreddiamonds.

Additional features and advantages of the invention will be set forth inthe description which follows, and will be apparent, in part, from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof, as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, anembodiment of the invention includes a nozzle, such as that used forhigh-pressure water jet machining, comprising a single-crystal diamond,wherein the single-crystal diamond was produced by a method comprisingcontrolling the temperature of a growth surface of the diamond such thatthe temperature of the growing diamond crystals is in the range of900-1400° C., the diamond is mounted in a heat sink holder made of amaterial that has a high melting point and high thermal conductivity tominimize temperature gradients across the growth surface of the diamond,growing single-crystal diamond by microwave plasma chemical vapordeposition on the growth surface of a diamond in a deposition chamberhaving an atmosphere greater than 150 torr, wherein the atmospherecomprises from about 8% to in excess of about 30% CH₄ per unit of H₂. Inone embodiment, the heat sink holder used to produce the diamondcomprises molybdenum. In another embodiment, all temperature gradientsacross the growth surface of the diamond are less than about 30° C. Inanother embodiment, all temperature gradients across the growth surfaceof the diamond are less than about 20° C. In another embodiment, thesingle-crystal diamond is produced by a method further comprising theuse of from about 5 to about 25% O₂ per unit of CH₄ in the depositionchamber atmosphere.

The single-crystal diamonds that have the characteristics described inthe preceding paragraph have additional uses, which include, but are notlimited to the following:

-   a.) wear resistant material—including, but not limited to,    water/fluid jet nozzles, cutting instruments (e.g., razors, knives),    surgical instruments (e.g., surgical blades, cutting blades for    surgical instruments), microtone, hardness indentor, graphical    tools, stichels, instruments used in the repair of lithographic    pieces, missile radomes, bearings, including those used in    ultra-high speed machines, diamond-biomolecule devices, microtomes,    and hardness indentors;-   b.) optical parts—including, but not limited to, optical windows,    reflectors, refractors, lenses, gratings, etalons, alpha particle    detectors, and prims;-   c.) electronics—including, but not limited to, microchannel cooling    assemblies; high purity SC-CVD diamonds for semiconductor    components, SC-CVD doped with impurities for semiconductor    components-   d.) anvils in high pressure apparatuses—including, but not limited    to, the “Khvostantsev” or “Paris-Edinburgh” toroid shaped anvils    that can be used with multiple optical, electrical, magnetic, and    acoustic sensors; Bridgman anvils that are relatively large, have    variable heights, and include major angles [15]; Multianviles,    Drickamer cells, belt apparatus, piston-cylinder apparatus;    precompressing samples for laser or magnetic shock wave studies;    colorless, smooth coating for hydrogen and other applications,    apparatus for pre-compressing samples for lasers or magnetic shock;-   e.) containers—including, but not limited to, 6 edge {100} plated    diamonds can be connected to each other to form a container, CVD    diamond coating can be further employed to form a vacuum tight    container;-   f.) laser source—including, but not limited to, annealing SC-CVD    diamond to form a stable H3 center (nitrogen aggregate, N-V center,    Si center, or other dopants;-   g.) superconductor and conducting diamond—including, but not limited    to, HPHT annealing with SC-CVD diamond grown with an impurity such    as H, Li, N, Mg, or another low atomic weight element with a size    approaching that of carbon;-   h.) substrate for other CVD diamond growth—using CVD plates as    substrates for CVD growth has the advantage over natural or HPT    substrates in large size and toughness (to avoid cracking during    growth).

In one embodiment, for example, the invention is directed to a cuttingblade for a surgical instrument comprising a cutting edge comprising asingle-crystal diamond, wherein the single-crystal diamond was producedby a method comprising controlling temperature of a growth surface ofthe diamond such that the temperature of the growing diamond crystals inthe range of 900-1400° C., the diamond is mounted in a heat sink holdermade of a material, including, but not limited to, molybdenum tominimize temperature gradients across the growth surface of the diamond(e.g., to less than about 20° C.), growing single-crystal diamond bymicrowave plasma chemical vapor deposition on the growth surface of adiamond in a deposition chamber having an atmosphere greater than 150torr, wherein the atmosphere comprises from about 8% to in excess ofabout 30% CH₄ per unit of H₂.

In another embodiment, the invention is directed to a cutting instrumentcomprising a cutting edge comprising a single-crystal diamond, whereinthe single-crystal diamond was produced by a method comprisingcontrolling temperature of a growth surface of the diamond such that thetemperature of the growing diamond crystals in the range of 900-1400°C., the diamond is mounted in a heat sink holder made of a material,including, but not limited to, molybdenum to minimize temperaturegradients across the growth surface of the diamond (e.g., to less thanabout 20° C.), growing single-crystal diamond by microwave plasmachemical vapor deposition on the growth surface of a diamond in adeposition chamber having an atmosphere greater than 150 torr, whereinthe atmosphere comprises from about 8% to in excess of about 30% CH₄ perunit of H₂.

In another embodiment, the invention is directed to a wire drawing diecomprising a single-crystal diamond, wherein the single-crystal diamondwas produced by a method comprising controlling temperature of a growthsurface of the diamond such that the temperature of the growing diamondcrystals in the range of 900-1400° C., the diamond is mounted in a heatsink holder made of a material, including, but not limited to,molybdenum to minimize temperature gradients across the growth surfaceof the diamond (e.g., to less than about 20° C.), growing single-crystaldiamond by microwave plasma chemical vapor deposition on the growthsurface of a diamond in a deposition chamber having an atmospheregreater than 150 torr, wherein the atmosphere comprises from about 8% toin excess of about 30% CH₄ per unit of H₂

In another embodiment, the invention is directed to a bearing comprisinga single-crystal diamond, wherein the single-crystal diamond wasproduced by a method comprising controlling temperature of a growthsurface of the diamond such that the temperature of the growing diamondcrystals in the range of 900-1400° C., the diamond is mounted in a heatsink holder made of a material, including, but not limited to,molybdenum to minimize temperature gradients across the growth surfaceof the diamond (e.g., to less than about 20° C.), growing single-crystaldiamond by microwave plasma chemical vapor deposition on the growthsurface of a diamond in a deposition chamber having an atmospheregreater than 150 torr, wherein the atmosphere comprises from about 8% toin excess of about 30% CH₄ per unit of H₂.

In another embodiment, the invention is directed to a diamond anvilcomprising a single-crystal diamond, wherein the single-crystal diamondwas produced by a method comprising controlling temperature of a growthsurface of the diamond such that the temperature of the growing diamondcrystals in the range of 900-1400° C., the diamond is mounted in a heatsink holder made of a material, including, but not limited to,molybdenum to minimize temperature gradients across the growth surfaceof the diamond (e.g., to less than about 20° C.), growing single-crystaldiamond by microwave plasma chemical vapor deposition on the growthsurface of a diamond in a deposition chamber having an atmospheregreater than 150 torr, wherein the atmosphere comprises from about 8% toin excess of about 30% CH₄ per unit of H₂.

In another embodiment, the invention is directed to an etalon comprisinga single-crystal diamond, wherein the single-crystal diamond wasproduced by a method comprising controlling temperature of a growthsurface of the diamond such that the temperature of the growing diamondcrystals in the range of 900-1400° C., the diamond is mounted in a heatsink holder made of a material, including, but not limited to,molybdenum to minimize temperature gradients across the growth surfaceof the diamond (e.g., to less than about 20° C.), growing single-crystaldiamond by microwave plasma chemical vapor deposition on the growthsurface of a diamond in a deposition chamber having an atmospheregreater than 150 torr, wherein the atmosphere comprises from about 8% toin excess of about 30% CH₄ per unit of H₂.

In another embodiment, the invention is directed to an optical windowcomprising a single-crystal diamond, wherein the single-crystal diamondwas produced by a method comprising controlling temperature of a growthsurface of the diamond such that the temperature of the growing diamondcrystals in the range of 900-1400° C., the diamond is mounted in a heatsink holder made of a material, including, but not limited to,molybdenum to minimize temperature gradients across the growth surfaceof the diamond (e.g., to less than about 20° C.), growing single-crystaldiamond by microwave plasma chemical vapor deposition on the growthsurface of a diamond in a deposition chamber having an atmospheregreater than 150 torr, wherein the atmosphere comprises from about 8% toin excess of about 30% CH₄ per unit of H₂.

In another embodiment, the invention is directed to an alpha particledetector comprising a single-crystal diamond, wherein the single-crystaldiamond was produced by a method comprising controlling temperature of agrowth surface of the diamond such that the temperature of the growingdiamond crystals in the range of 900-1400° C., the diamond is mounted ina heat sink holder made of a material, including, but not limited to,molybdenum to minimize temperature gradients across the growth surfaceof the diamond (e.g., to less than about 20° C.), growing single-crystaldiamond by microwave plasma chemical vapor deposition on the growthsurface of a diamond in a deposition chamber having an atmospheregreater than 150 torr, wherein the atmosphere comprises from about 8% toin excess of about 30% CH₄ per unit of H₂.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a diagram of a diamond production apparatus according to anembodiment of the present invention in which a cross-section ofdeposition apparatus with a specimen holder assembly for holding thediamond stationary during a diamond growth process is depicted.

FIG. 2 a is a perspective view of the deposition apparatus shown in FIG.1.

FIG. 2 b is a perspective view of the diamond and sheath shown in FIG.1.

FIG. 3 is a diagram of a diamond production apparatus according to anembodiment of the present invention in which a cross-section of adeposition apparatus with a specimen holder assembly for moving thediamond during the diamond growth process is depicted.

FIGS. 4 a-4 c depicts a cross-sectional views of holders or thermalmasses that can be used in accordance with the present invention.

FIG. 5 is a diagram of a diamond production apparatus according toanother embodiment of the present invention in which a cross-section ofa deposition apparatus with a specimen holder assembly for moving thediamond during the diamond growth process is depicted.

FIG. 6 is a flow diagram illustrating a process 600 in accordance withembodiments of the present invention that can be used with the specimenholder assembly shown in FIG. 1.

FIG. 7 is a flow diagram illustrating a process 700 in accordance withembodiments of the present invention that can be used with the specimenholder assembly shown in FIG. 3 or with the specimen holder assemblyshown in FIG. 5.

FIG. 8 is a UV-VIS spectrum for an HPHT IIa diamond; an SC-CVD diamondproduced according to the method of the invention, e.g., with adeposition chamber atmosphere comprising from about 5% to about 25% O₂per unit of CH₄; and an SC-CVD diamond produced with N₂ gas present as acomponent of the deposition chamber atmosphere.

FIG. 9 is photograph of a substantially colorless SC-CVD crystal grownaccording to the method of the invention, e.g., with a depositionchamber atmosphere comprising from about 5% to about 25% O₂ per unit ofCH₄, and an SC-CVD crystal grown with N₂ gas present as a component ofthe deposition chamber atmosphere.

FIG. 10 is an SC-CVD diamond block formed by deposition on six {100}faces of an HPHT Ib substrate.

FIG. 11 is an IR absorption spectrum (2500-8000 cm⁻¹) for an SC-CVDdiamond produced according to the method of the invention, e.g., with adeposition chamber atmosphere comprising from about 5% to about 25% O₂per unit of CH₄, and an SC-CVD diamond produced with N₂ gas present as acomponent of the deposition chamber atmosphere.

FIG. 12 shows a cross-section of a water jet cutting apparatus.

FIG. 13 shows a cubic container configuration comprised of CVD diamond.

FIG. 14 shows CVD diamond grown on two plates placed together in stepconfiguration.

FIG. 15 a) shows a diamond anvil cell and gasket supported with abinding ring

FIG. 15 b) shows a beveled diamond anvil.

DETAILED DESCRIPTION

Reference will now be made in detail to methods of producing diamondused in the applications of the invention. FIG. 1 is a diagram of adiamond production system 100 according to an embodiment of the presentinvention, in which a deposition apparatus 102 is depicted incross-section. The diamond production system 100 includes a MicrowavePlasma Chemical Vapor Deposition (MPCVD) system 104 that contains adeposition apparatus 102 as well as reactant and plasma controls 106.For example, the MPCVD system 104 can be a SEKI AX6550 made by SekiTechnotron Corp. Tokyo, Japan. This system is capable of producing 6kilowatts of power output at a frequency of 2.45 GHz. As anotherexample, the MPCVD system 104 can be a SEKI AX5250 made by SekiTechnotron Corp. This system is capable of producing 5 kilowatts ofpower output at a frequency of 2.45 GHz. As another example, the MPCVDsystem 104 can be a WAVEMAT MPDR 330 313 EHP made by Wavemat, Inc. Sucha MPCVD system is capable of producing a 6-kilowatt power output at afrequency of 2.45 GHz, and has a chamber volume of approximately 5,000cubic centimeters. However, the MPCVD system specifications can varywith the scale of a deposition process in terms of size of thedeposition area and/or rate of deposition.

The MPCVD system 104 includes a chamber within the deposition apparatus102 that is at least in part defined by a bell jar 108, which is used insealing the chamber. Prior to MPCVD operations, the air within thechamber is withdrawn. For example, a first mechanical type of vacuumpump is used to draw down the chamber and then a second high vacuum typeof vacuum pump, such as a turbopump or cryopump, further draws out theair inside the chamber. Plasma is generated within the chamber by a setof plasma electrodes spaced apart within the chamber. Neither the pumpsnor the plasma electrodes are illustrated in FIG. 1.

The deposition apparatus 102 also includes a specimen holder assembly120 installed within the chamber of the MPCVD system 104. Typically, aspecimen holder assembly is positioned in the center of the depositionchamber floor 122 of the deposition apparatus 102, as shown in FIG. 1.The specimen holder assembly 120 shown in FIG. 1 is illustrated incross-section. The specimen holder assembly 120 can include a stage 124installed in the floor of the deposition apparatus 102.

As shown in FIG. 1, the stage 120 can be attached to the depositionchamber floor 122 using bolts 126 a and 126 c. The stage 124 can bemolybdenum or any other type of material having a high thermalconductivity and high melting point. In addition, the stage 124 can becooled during the process of growing diamond by a coolant passingthrough a coolant pipe 128 within the stage 124. The coolant can bewater, a refrigerant or other types of fluid with sufficient heatcarrying capacity to cool the stage. Although the coolant pipe is shownas having a U-shaped path through the stage 124 in FIG. 1, the coolantpipe 128 can have a helically shaped path or other types of paths withinthe stage 124 to more efficiently cool the stage 124.

Positioned on the stage 124 of the specimen holder assembly 120, asshown in FIG. 1, is a set ring 130 having set screws, such as screws 131a and 131 c, for tightening collets 132 a and 132 b around a sheath 134that holds diamond 136. The sheath 134 is a holder, which makes athermal contact with a side surface of the diamond 136 adjacent to anedge of a top surface of the diamond 136. Because collets 132 a and 132b are tightened onto the sheath 134 by screws 131, the sheath 134 holdsthe diamond 136 in a stationary position and acts as a heat-sink toprevent the formation of twins or polycrystalline diamond along theedges of the growth surface of the diamond 136.

The diamond 136 can include a diamond seed portion 138 and a growndiamond portion 140. The diamond seed portion 138 can be a manufactureddiamond or a natural diamond. In one embodiment, the seed is a member ofa group consisting of a natural, colorless Ia diamond; a colorless 11 adiamond; an HPHT synthetic yellow Ib diamond; and an SC-CVD diamond. Inanother embodiment, the seed is an SC-CVD diamond. In anotherembodiment, the seed is an SC-CVD diamond that has {100} faces. Inanother embodiment, the seed is an SC-CVD diamond that has six {100}faces. In another embodiment, all top {100} surfaces of the seed haveareas from about 1 to about 100 mm².

As shown in FIG. 1, the top surface or growth surface of the diamond 136is positioned within a region of the plasma 141 having a resonant powerat a height H above the deposition chamber floor 122. The resonant powercan be the maximum resonant power within the plasma 141 or a degreethereof. The top surface or growth surface of the diamond 136 isinitially the diamond seed portion 138 and is then the grown diamondportion 140 as the diamond grows.

As shown in FIG. 1, the top edge of the sheath 134 is at a distance Djust below the top surface or top edges of the diamond 136. The distanceD should be sufficiently large enough to expose the edges of the growthsurface of the diamond 136 to the plasma 141. However, the distance Dcan not be so large as to prevent the heat-sinking effect of the sheath134 that prevents the formation of twins or polycrystalline diamondalong the edges of the growth surface of the diamond 136. Thus, D shouldbe within a specified distance range, such as 0-1.5 mm. The distance Dand the height H, as shown in FIG. 1, are manually set using the screws131 of the set ring 130 by positioning the diamond 136 in the sheath,positioning the sheath in the collets 132 a and 132 b, and thentightening the screws 131.

FIG. 2 is a perspective view of the deposition apparatus shown inFIG. 1. In the center of the deposition chamber floor 122 of FIG. 2 is acircular stage 124 with a central recess 125. As shown in FIG. 2, thestage 124 is held in position by bolts 126 a-126 d. The stage 124 can beformed of molybdenum or other materials having a high thermalconductivity and high melting point. A set ring 130 with four screws 131a-131 b is positioned within the recess 125 of the stage 124 along withcollets 132 a-132 b. In the alternative, the set ring 130 can be boltedto the stage 124 to increase thermal conductance between the stage andthe set ring.

As shown in FIG. 2 a, a rectangular sheath 134, which can either be ashort length of rectangular tubing or a sheet folded into a rectangle,is positioned in the collets 132 a and 132 b with a diamond 136 therein.The sheath 124 can be molybdenum or any other type of material having ahigh thermal conductivity and high melting point. The screws 131 a-131 dare tightened on the collets 132 a-132 b such that the sheath 134 istightened onto the diamond 136 such that the sheath 134 acts as a heatsink on the four side surfaces of the diamond 136. As shown in FIG. 1,the sheath 134 also makes thermal contact to the stage 124. The collets132 a-132 b make thermal contact with the stage 124 and serve as thermalmasses for transferring heat from the sheath 134 into the stage 124. Thetightening of the sheath 134 onto the diamond 136 increases the qualityof the thermal contact between the diamond and the sheath. As shown inFIG. 1, the sheath 134 can also make thermal contact to the stage 124.Although a rectangular shape is shown in FIG. 2 a for both the sheathand the diamond, the sheath and the diamond can have any geometric shapesuch as elliptical, circular or polygonal. The shape of the sheath orholder should be substantially the same as the diamond.

In the exemplary embodiment of the invention shown in FIGS. 1 and 2 a,the stage 124 can have a diameter of approximately 10.1 cm. and thesheath 134 can be approximately 2.5 cm wide. Regardless of thedimensions selected for the stage and the sheath 134, the thermal massof the stage 122, sheath 124, and collets 132 can be adjusted to providean optimal heat sink for the diamond 136. Additionally, the path andextent of the coolant pipes 128 can be modified for greater coolingeffect, especially if a particularly large diamond is to be produced.Further, a refrigerant or other low temperature fluids can be used as acoolant.

Molybdenum is only one potential high thermal conductivity, high meltingpoint material used in the stage 124, set ring 130, collets 132, sheath134 and other components. Molybdenum is suitable for these componentsbecause it has a high melting point, which is 2617° C., and a highthermal conductivity, which is 1.38 W/cm K at 298.2 K. In addition, alarge graphite build-up does not tend to form on molybdenum. Othermaterials, such as molybdenum-tungsten alloys or engineered ceramics,having high melting points above the process temperature and a thermalconductivity comparable to that of molybdenum, can alternatively be usedinstead of molybdenum. Additional materials which have theaforementioned high melting point and high thermal conductivities andcan be used in the methods and apparatuses of the invention include, butare not limited to, chromium, iridium, niobium, platinum, rhenium,rhodium, ruthenium, silicon, tantalum, tungsten, and mixtures thereof.

Returning to FIG. 1, another component of the diamond production system100 is an noncontact measurement device, such as an infrared pyrometer142, which is used to monitor the temperature of the diamond seed 138and later the grown diamond 140 during the growth process withoutcontacting the diamond 136. The infrared pyrometer 142 can be, forexample, a MMRON M77/78 two color infrared pyrometer from MikronInstruments, Inc. of Oakland, N.J. The infrared pyrometer 142 is focusedon the diamond seed 138 or later on the grown diamond 140 with a targetarea measure of 2 mm. By using the infrared pyrometer 142, thetemperature of the growth surface of the diamond 136 is measured towithin 1° C.

The diamond production system 100 of FIG. 1 also includes an MPCVDprocess controller 144. The MPCVD process controller 144 is typicallyprovided as a component of the MPCVD system 104. As is well-known in theart, the MPCVD process controller 144 exercises feedback control over anumber of MPCVD parameters, including, but not limited to, the processtemperature, gas mass flow, plasma parameters, and reactant flow ratesby using the reactant and plasma controls 106. The MPCVD processcontroller 144 operates in cooperation with a main process controller146. The main process controller 146 takes input from the MPCVDcontroller 144, the infrared pyrometer 142, and from other measuringdevices of other components in the diamond production system 100 andcarries out executive-level control over the process. For example, themain process controller 146 can measure and control coolant temperaturesand/or flow rates of the coolant in the stage using a coolant controller148.

The main process controller 146 can be a general purpose computer, aspecial purpose computing system, such as an ASIC, or any other knowntype of computing system for controlling MPCVD processes. Depending onthe type of main process controller 146, the MPCVD process controller144 can be integrated into the main process controller so as toconsolidate the functions of the two components. For example, the mainprocess controller 146 can be a general purpose computer equipped withthe LabVIEW programming language from National Instruments, Inc. ofAustin, Tex. and the LabVIEW program such that the general purposecomputer is equipped to control, record, and report all of the processparameters.

The main process controller 146 in FIG. 1 controls the temperatures ofthe growth surface such that all the temperature gradients across thegrowth surface of the diamond are less than or equal to 20° C. Precisecontrol over growth surface temperatures and growth surface temperaturegradients prevents the formation of polycrystalline diamond or twinssuch that a large single-crystal diamond can be grown. The ability tocontrol all of the temperature gradients across the growth surface ofthe diamond 136 is influenced by several factors, including the heatsinking capability of the stage 124, the positioning of the top surfaceof the diamond in the plasma 141, the uniformity of the plasma 141 thatthe growth surface of the diamond is subjected to, the quality ofthermal transfer from edges of the diamond via the holder or sheath 134to the stage 124, the controllability of the microwave power, coolantflow rate, coolant temperature, gas flow rates, reactant flow rate andthe detection capabilities of the infrared pyrometer 142. Based upontemperature measurements from the pyrometer 142, the main processcontroller 146 controls the temperature of the growth surface such thatall temperature gradients across the growth surface are less than 20° C.by adjusting at least one of microwave power to the plasma 141, thecoolant flow rate, coolant temperature, gas flow rates and reactant flowrate.

FIG. 2 b is a perspective view of the diamond 136 shown in FIG. 1depicting exemplary points P1, P2, P3 and P4 along the growth surface137 of the diamond 136. FIG. 2 b also depicts the distance D between thegrowth surface 137 or top edges 139 of the diamond 136 and an edge 135of the sheath 134. Typically, large temperature variations, in terms oftemperature differences across the growth surface, occur between theedges and the middle of the growth surface of the diamond. For example,larger temperature gradients occur between the points P1 and P2 thanoccur between the points P1 and P3. In another example, largertemperature gradients occur between the points P4 and P2 than occurbetween the points P4 and P3. Thus, controlling temperature of thegrowth surface of the diamond such that all temperature gradients acrossthe growth surface are less than 20° C. should at least take intoaccount a temperature measurement between the middle and an edge 139 ofthe growth surface 137. For example, the main controller 146 may controlthe temperature of the growth surface such that the temperature gradientbetween points P1 and P2 is less than 20° C.

The spot size of the infrared pyrometer can affect the ability tomonitor temperature gradients across the top surface of the diamond andthus the growth rate of the diamond. For example, if the size of thediamond is large in comparison to the spot size of the infraredpyrometer, the temperature at each of the edges of the growth surface ofthe diamond can be outside of the field of view of the infraredpyrometer. Thus, multiple infrared pyrometers should be used for adiamond with a large growing area. Each of the multiple pyrometersshould be focused on different edges about the surface of the diamondand preferably near the corners, if any. Thus, the main processcontroller 146, as shown in FIG. 1, should be programmed to integrateoverlapping fields of view from the multiple pyrometers to produce acontiguous “map” of the temperatures across the diamond's surface orinterpolate between non-overlapping fields of view to a produce aninterpreted “map” of the temperatures across the diamond's growthsurface. In the alternative, the temperature gradient between a singleedge or corner point with respect to the middle of the growth surfacecan be monitored as indicative of the maximum temperature gradient thatexists across the growth surface of the diamond.

In addition to the infrared pyrometer 142 for temperature control, otherprocess control instrumentation may be included in the diamondproduction system 100. Additional process control instrumentation caninclude equipment for determining the type and quality of the diamond136 while the growth process is underway. Examples of such equipmentinclude visible, infrared, and Raman spectrometers, which are optical innature and can be focused on the same point as the infrared pyrometer142 to obtain data on the structure and quality of the diamond whilegrowth is underway. If additional equipment is provided, it can beconnected to the main process controller 146 such that the main processcontroller 146 controls the instrumentation and presents the results ofthe analytical methods along with other status information. Additionalprocess control instrumentation may be particularly useful inexperimental settings, in “scaling up” a process to produce largerdiamonds, and in quality control efforts for an existing diamondproduction system 100 and corresponding process.

As the diamond 136 grows, both the distance D and the height H increase.As the distance D increases, the heat-sinking capacity of the sheath 134for the top edges 139 of the growth surface of the diamond 136 reduces.In addition, characteristics of the plasma, such as temperature and/orconsistency, change as the growth surface of the diamond 136 extendsinto the plasma 141. In the diamond production system 100, the growthprocess is periodically halted so that the position of the diamond 136can be adjusted downward with respect to the sheath 134 to reduce thedistance D, and both the diamond 136 and the sheath 134 can be adjusteddownward with respect to the deposition chamber floor 122 to reduce theheight H. This repositioning allows the diamond growth on the growthsurface of the diamond 136 to occur within a desired region of resonantpower within the plasma 141, allows the infrared pyrometer 142 and anyadditional instruments to remain focused on the growth surface of thediamond 136, and has the effect of maintaining an efficient thermalcontact for sinking heat from the edges of the growth surface of thediamond 136.

FIG. 3 is a diagram of a diamond production apparatus 300 according toan embodiment of the present invention in which a cross-section ofdeposition apparatus 304 with a specimen holder assembly 320 for movingthe diamond 136 during the diamond growth process is depicted. Some ofthe components of diamond production apparatus 300 are substantially thesame as those of diamond production system 100, and thus the discussionabove with regard to FIG. 1 will suffice to describe those componentslikewise numbered in FIG. 3. For example, the pyrometer 142, depositionchamber floor 122, coolant pipe 128 and bell jar 108 in FIG. 3 aresubstantially the same as those described in FIG. 1.

As shown in FIG. 3, the diamond 136 is mounted on a diamond actuatormember 360 within the sheath 134 of the specimen holder assembly 320.The diamond 136 is slidably mounted within the sheath 134 on a diamondactuator member 360 that translates along an axis substantiallyperpendicular to the growth surface. The diamond actuator member 360protrudes through a stage 324 and is controlled from underneath thestage 324 with a diamond control, which is shown as a part of thecoolant and diamond/holder controls 329 in FIG. 3. The diamond actuatormember 360 is for setting the height H between the growth surface of thediamond 136 and the deposition chamber floor 122. Although the diamondactuator member 360 in FIG. 3 is shown as a threaded rod, the diamondactuator member can be of any geometric shape that enables positioningof the diamond 136 at height or position above the deposition chamberfloor. Those skilled in the art will realize that components placedwithin the bell jar, such as the diamond actuator member 360, should bevacuum compatible so as to avoid problems in maintaining the desiredatmosphere.

The actuator (not shown) for the diamond actuator member 360 is a motor(not shown). However, the actuator can be any one of a number of knowntypes of actuator, depending on the size of diamond that is to be grown,the growth rate, and the level of movement precision required. Forexample, if the diamond 136 is small in size, a piezoelectric actuatormay be used. If the diamond 136 is relatively large or can be grownrelatively large, a motorized computer-controllable actuator ispreferred. Regardless of the particular actuator employed, the mainprocess controller 346 controls the movement of the diamond actuatormember 360 so that the diamond 136 can be automatically moved downwardas diamond growth progresses.

In addition, a holder actuator member 362 protrudes through the stage324 and is controlled from underneath the stage 324 with holder control,which is shown as a part of the coolant and diamond/holder controls 329in FIG. 3. The holder actuator member 362 translates along an axissubstantially perpendicular to the growth surface and is for maintainingthe distance D between an edge of the growth surface of the diamond 136and a top edge of the holder or sheath 134. A diamond production systemcan have a diamond actuator member, a holder actuator member, or acombination of both.

The holder actuator member 362 in FIG. 3 is threaded into the stage 324and the diamond actuator member 360 is threaded into the holder actuatormember 362. By this arrangement, the diamond and holder controls of thecoolant and diamond/holder controls 329 shown in FIG. 3 can move thediamond 136, the sheath 134, or both the sheath 134 and the diamond 136.Although the holder actuator member 362 in FIG. 3 is shown as a threadedcylinder with threading on the inside for the diamond actuator member360 and threads on the outside for threading into the stage 324, theholder actuator member can be of any geometric shape that enablesmaintaining a specified distance range between an edge of the growthsurface of the diamond 136 and the top edge of the holder or sheath 134.Those skilled in the art will realize that components placed within thebell jar, such as the holder actuator member 362 or a combination ofboth the holder actuator member and the diamond actuator member, shouldbe vacuum compatible so as to avoid problems in maintaining the desiredatmosphere.

As shown in FIG. 3, a thermal mass 364 is positioned within a recess ofthe stage 324. The holder or sheath 134 is slidably positioned withinthermal mass 364 such that thermal energy is transferred from the sheath134 to the stage 324. The top surface of the thermal mass 364 can becontoured such that heat can be transferred from the sheath 134 whileminimizing the electrical effect of the thermal mass 364 on the plasma341. Thermal masses 466 a, 466 b and 466 c in FIGS. 4 a-4 c,respectively, are examples of other contoured thermal masses withdifferent cross-sectional shapes, which in the alternative, can be usedin lieu of the thermal mass 364 shown in FIG. 3. A thermal mass can bemade of molybdenum. Other materials, such as molybdenum-tungsten alloysor engineered ceramics, having high melting points above the processtemperature and a thermal conductivity comparable to that of molybdenumcan be used as a thermal mass for transferring heat from a side of thediamond to a stage.

By minimizing the electrical effect of thermal mass 364 on the plasma341, the region within the plasma 341 in which the diamond is grown willbe more uniform. In addition, higher pressure can be used in growingdiamond, which will increase the growth rate of single-crystal diamond.For example, pressures can vary from about 100 torr to about 400 torr,and single-crystal growth rates can be from 50 to 300 microns per hour.Using a higher pressure (above 400 torr) is possible because theuniformity, shape and/or position of the plasma 341 are not as readilyaffected by thermal mass 364, which is contoured to remove heat from theedges of the growth surface of the diamond and minimizes the electricaleffect of the thermal mass 364 on the plasma 341. In addition, lessmicrowave power, such as 1-2 kW, is needed to maintain the plasma 341.Otherwise, a lower pressure and/or increased microwave power would haveto be used to maintain the uniformity, shape and/or position of theplasma 341.

As the diamond 136 grows, both the distance D and the height H increase.As the distance D increases, the heat-sinking capacity of the sheath 134for the top edges of the growth surface of the diamond 136 decreases. Inaddition, characteristics of the plasma, such as temperature, change asthe growth surface of the diamond 136 extends into the plasma 341. Inthe diamond production system 300, the growth process is halted when thediamond 136 reaches a predetermined thickness since the distance D andthe height H can be controlled by the main process controller 346, viathe coolant and diamond/holder controls 329, using the holder actuatormember 362 and diamond actuator member 360 during the diamond growingprocess. This repositioning, either manually or automatically undercontrol of the controller 144, allows the diamond growth on the growthsurface of the diamond 136 to occur within a desired region of resonantpower within the plasma 341. Further, repositioning allows the infraredpyrometer 142 and any additional instruments to remain focused on thegrowth surface of the diamond 136, and can maintain an efficient sinkingof heat from the edges of the growth surface of the diamond 136.

FIG. 5 is a diagram of a diamond production apparatus 500 according toan embodiment of the present invention in which a cross-section ofdeposition apparatus 504 with a specimen holder assembly 520 for movingthe diamond 136 during the diamond growth process is depicted. Some ofthe components of diamond production apparatus 500 are substantially thesame as those of diamond production system 100 and 300, and thus, thediscussion above with regard to FIG. 1 and FIG. 3 will suffice todescribe those components likewise numbered in FIG. 5. For example, thepyrometer 142, deposition chamber floor 122, coolant pipe 128 and belljar 108 in FIG. 5 are substantially the same as those described inFIG. 1. In another example, the coolant and diamond/holder controller329 and diamond actuator member 360 in FIG. 5 are substantially the sameas those in FIG. 3.

As shown in FIG. 5, the diamond 136 is mounted on the diamond actuatormember 360 and within a contoured thermal mass 566, which acts as aholder. By placing the diamond 136 directly within the contoured thermalmass 566, thermal efficiencies for heat-sinking the diamond 136 areincreased. However, the plasma 541 may be more easily affected since thewhole contoured thermal mass is moved by the holder actuator 562 in thestage 524 with a diamond holder control, which is shown as a part of thecoolant and diamond/holder controls 329 in FIG. 3. Thus, the mainprocess controller 546 should take into account such a factors forappropriately controlling the plasma and/or other parameters of thegrowth process. In the alternative, the convex thermal mass 364 shown inFIG. 3, the slant-sided thermal mass 466 b in FIG. 4 b, aslant-sided/cylindrical apex thermal mass 466 c in FIG. 4 c or othergeometric configurations can be used in lieu of the concave thermal mass566, in FIG. 5.

FIG. 6 is a flow diagram illustrating a process 600 in accordance withembodiments of the present invention that can be used with specimenholder assembly shown in FIG. 1. The process 600 begins with step S670in which an appropriate seed diamond or a diamond in the process ofbeing grown is positioned in a holder. In the specimen holder assembly120 of FIG. 1 for example, the diamond seed portion 138 is placed in asheath 134 and the screws 131 a-131 d are tightened by an operator.Other mechanisms can be used to maintain both the sheath and diamond inposition, such as spring loaded collets, hydraulics or other mechanismscan be used in exerting a force against the holder or sheath.

As referred to in step S672, the temperature of the growth surface ofthe diamond, either the diamond seed or grown diamond, is measured. Forexample, the pyrometer 142 in FIG. 1 takes a measurement of the growthsurface, which is the top surface of the growing diamond portion 140,and provides the measurement to the main process controller 146. Themeasurement is taken such that a thermal gradient across the growthsurface of the diamond 136 can be determined by the main processcontroller or at least the temperature of an edge of the growth surfaceof the diamond are inputted into the main process controller.

The main process controller, such as main process controller 146 shownin FIG. 1, is used in controlling the temperature of the growth surface,as referred to in S674 in FIG. 6. The main process controller controlsthe temperature by maintaining thermal gradients of less than 20° C.across the growth surface. While controlling the temperature of thegrowth surface, a determination is made to whether the diamond should berepositioned in the holder, as shown in step S675 of FIG. 6. If the maincontroller can not control the temperature of the growth surface of thediamond such that all temperature gradients across the growth surfaceare less than 20° C. by controlling the plasma, gas flows and coolantflows, then the growth process is suspended so that the diamond can berepositioned in the holder, as shown in step S678 of FIG. 6, for betterheat-sinking of the diamond and/or better positioning of the diamondwithin the plasma. If the main controller can maintain all of thethermal gradients across the growth surface of the diamond to be lessthan 20° C., then the growing of the diamond on the growth surfaceoccurs as shown in step S676 of FIG. 6.

Measuring the temperature of a growth surface of the diamond,controlling temperature of the growth surface and growing diamond on thegrowth surface occurs until it is determined that the diamond should berepositioned, as shown in FIG. 6. Although measuring, controlling,growing and the acts of determining are shown and described as steps,they are not necessarily sequential and can be concurrent with oneanother. For example, the step of growing diamond on the growth surfacecan occur while measuring the temperature of a growth surface of thediamond and controlling temperature of the growth surface are occurring.

The repositioning of the diamond, as referred to in step S678, can bedone manually or with a robotic mechanism. In addition, a determinationcan be made of whether the diamond has reached a predetermined ordesired thickness, as shown in step S673 of FIG. 6. The determinationcan be based on an actual measurement via mechanical or optical devices.In another example, the determination can be based on the length ofprocessing time in view of known growth rates for the process. If thediamond has reached the predetermined thickness, then the growingprocess is complete, as referred to by step 680 in FIG. 6. If thediamond has not reached the predetermined thickness, then the growthprocess is started again and continues with measuring the temperature ofa growth surface of the diamond, controlling temperature of the growthsurface and growing diamond on the growth surface until it is determinedthat the diamond needs to be repositioned, as shown in FIG. 6.

FIG. 7 is a flow diagram illustrating a process 700 in accordance withembodiments of the present invention that can be used with specimenholder assembly shown in FIG. 3 and FIG. 5. The process 700 begins withstep S770 in which an appropriate seed diamond, which can be a growndiamond, manufactured diamond, natural diamond or combination thereof,is positioned in a holder. In the specimen holder assembly 320 of FIG.3, for example, the diamond seed portion 138 is placed within sheath 134on the diamond actuator member 360, as shown in FIG. 3. In anotherexample of a specimen holder assembly, the diamond seed portion 138 isplaced within a contoured thermal mass 566 on the diamond actuator 360,as shown in FIG. 5.

As referred to in step S772, the temperature of the growth surface ofthe diamond, either the diamond seed or a newly grown diamond portion onthe diamond seed, is measured. For example, the pyrometer 142 in FIG. 3takes a measurement of the growth surface, which is the top surface ofthe growing diamond portion 140, and provides the measurement to themain process controller 346. In another example, the pyrometer 142 inFIG. 5 takes a measurement of the growth surface, which is the topsurface of the seed diamond portion 138, and provides the measurement tothe main process controller 546. The measurement is taken such thatthermal gradient across the growth surface of the diamond can bedetermined by the main process controller or at least the temperaturesof an edge and the middle of the growth surface are inputted into themain process controller.

A main process controller, such as main process controller 346 or 546,is used in controlling the temperature of the growth surface, asreferred to in S774 in FIG. 7. The main process controller controls thetemperature of the growth surface of the diamond such that alltemperature gradients across the growth surface are less than 20° C.While controlling the temperature of the growth surface, a determinationis made to whether the diamond needs to be repositioned in the holder,as shown in step S775 of FIG. 7. If the main controller can not maintainthe temperature of the growth surface of the diamond such that alltemperature gradients across the growth surface are less than 20° C. bycontrolling the plasma, gas flows and coolant flows, then the diamond isrepositioned while the diamond is growing as shown in FIG. 7 with the“YES” path from step S775 to both of steps S776 and S778. Byrepositioning the diamond within the holder, the heat-sinking of theedges of the growth surface is improved. In addition, the growth surfacecan be positioned within an optimal region of the plasma having aconsistency for maintaining all of the thermal gradients across thegrowth surface of the diamond to be less than 20° C. If the maincontroller can maintain all of the thermal gradients across the growthsurface of the diamond to be less than 20° C., then the growing of thediamond on the growth surface occurs without repositioning as shown inthe “NO” path from step S775 to step S776 of FIG. 7.

Measuring the temperature of a growth surface of the diamond,controlling temperature of the growth surface, growing diamond on thegrowth surface and repositioning the diamond in the holder occurs untilit is determined that the diamond has reached a predetermined thickness.As referred to in step S773 of FIG. 7, a determination is made ofwhether the diamond has reached a predetermined or desired thickness.The determination can be based on an actual measurement via mechanicalor optical devices. For example, a tracking program which records thedepth or the amount in terms of distance that the diamond had to berepositioned during the growth process. In another example, thedetermination can be based on the length of processing time in view ofknown growth rates for the growth process. If the diamond has reachedthe predetermined thickness, then the growing process is complete, asreferred to by step 780 in FIG. 7. If the diamond has not reached thepredetermined thickness, then the growth process continues withmeasuring the temperature of a growth surface of the diamond,controlling temperature of the growth surface, growing diamond on thegrowth surface and repositioning the diamond in the holder until it isdetermined that the diamond needs to be repositioned, as shown in the“NO” path from S773 to within S774 of FIG. 7.

When implementing processes 600 and 700, diamond growth is usuallycontinued as long as a “step growth” condition can be maintained. Ingeneral, the “step growth” condition refers to growth in which diamondis grown on the growth surface of the diamond 136 such that the diamond136 is smooth in nature, without isolated “outcroppings” or twins. The“step growth” condition may be verified visually. Alternatively, a lasercould be used to scan the growth surface of the diamond 136. A change inlaser reflectance would indicate the formation of “outcroppings” ortwins. Such a laser reflectance could be programmed into the mainprocess controller as a condition for stopping the growth process. Forexample, in addition to determining if the diamond is a predeterminedthickness, a determination can also be made of whether a laserreflectance is being received.

In general, the methods in accordance with exemplary embodiments of thepresent invention are designed to create large, colorless, high-qualitydiamonds with increased {100} growth rates, wherein the growth is alongthree dimensions. In one embodiment of the invention, oxygen is used inthe gas mix at a ratio of about 1-50% O₂ per unit of CH₄. In anotherembodiment of the invention, oxygen is used in the gas mix at a ratio ofabout 5-25% O₂ per unit of CH₄. Without wishing to be bound by theory,it is believed that the presence of oxygen in the gas mix of thedeposition chamber helps to reduce the incorporation of impurities inthe diamond, thus rendering the diamonds substantially colorless. Duringthe growth process, the methane concentration is in the range of about6-12%. A hydrocarbon concentration greater than about 15% may causeexcessive deposition of graphite inside the MPCVD chamber.

The process temperature may be selected from a range of about 700-1500°C., depending on the particular type of single-crystal diamond that isdesired or if oxygen is used. Polycrystalline diamond may be produced athigher temperatures, and diamond-like carbon may be produced at lowertemperatures. In one embodiment of the invention, the processtemperature may be selected from a range of about 700-1100° C. Inanother embodiment of the invention, the process temperature may beselected from a range of about 900-1100° C. During the growth process, apressure of about 100-400 torr is used. In one embodiment, a pressure ofabout 100-300 torr is used. In another embodiment, a pressure of about160-220 torr is used.

In one embodiment of the invention, the growth rate of thesingle-crystal diamond is greater than about 10 μm/hour. In anotherembodiment, the growth rate of the single-crystal diamond is greaterthan about 50 μm/hour. In another embodiment, the growth rate of thesingle-crystal diamond is greater than about 100 μm/hour.

In one embodiment of the invention, the single-crystal diamond grows tobe over 1.2 cm thick. In another embodiment of the invention, thesingle-crystal diamond grows to be over 5 carats in weight. In anotherembodiment of the invention, the single-crystal diamond grows to be over10 carats. In another embodiment of the invention, the single-crystaldiamond grows to be over 300 carats.

In one embodiment, the diamond is grown on up to six {100} faces of anSC-CVD diamond seed. In another embodiment, the diamond grown on up tosix {100} faces of the SC-CVD diamond seed is greater than about 300carats. In another embodiment, the growth of the diamond can besubstantially in two dimensions to produce a crystal of large lateraldimension (e.g., a plate of at least about one inch square) by polishingone of the longer surfaces and then growing the diamond crystal in asecond orthogonal direction on that surface. In another embodiment, thegrowth of the diamond can be in three dimensions. In another embodiment,the growth of the diamond is substantially cubic. In another embodiment,the substantially cubic diamond grown along three dimensions is at leastone inch in each dimension.

The gas mix can also include N₂. When N₂ is used, it is added to the gasmix at a ratio of about 0.2-3% N₂ per unit of CH₄. The addition of N₂ tothe gas mix at this concentration enhances the growth rate and promotes{100} face growth.

FIG. 8 is a UV-VIS spectrum for an HPHT 11 a diamond; an SC-CVD diamondproduced according to the method of the invention, e.g., with adeposition chamber atmosphere comprising from about 5% to about 25% O₂per unit of CH₄; and an SC-CVD diamond produced with N₂ gas present as acomponent of the deposition chamber atmosphere. The SC-CVD diamondproduced with N₂ gas is light brownish in appearance and exhibited abroad band around 270 nm. This is related to the presence of non-diamondcarbon, nitrogen, and vacancies in the diamond. SC-CVD diamonds producedwith N₂ gas that have a darker brown appearance show increasedabsorption below 500 nm and a broad feature centered at 520 nm. This isnot seen in natural diamond or HPHT-grown synthetic diamond. Thebrownish color and the broad band features can be removed by HPHTtreatment, e.g., annealing. The spectrum of the diamond produced by themethods of the invention, e.g., with a deposition chamber atmospherecomprising from about 5% to about 25% O₂ per unit of CH₄, did notexhibit a broad band at 270 nm or at 520 nm, and is comparable toman-made HPHT-type IIa diamond. Without wishing to be bound by theory,applicants believe that the added oxygen reduces the hydrogen impuritylevels and the amount of non-diamond carbon.

FIG. 9 shows a colorless SC-CVD diamond produced by the method of theinvention, e.g., with a deposition chamber atmosphere comprising fromabout 5% to about 25% O₂ per unit of CH₄, on the left and a brownishSC-CVD diamond produced with a N₂, rather than O₂, in the depositionchamber on the right. Both single-crystal diamonds are approximately5×5×1 mm in size.

FIG. 10 shows an SC-CVD diamond block formed by deposition on six {100}faces of a HPHT Ib substrate, such as the 4×4×1.5 mm crystal shownbelow. This is an attempt to further increase the size of the diamondcrystals, wherein gem-quality CVD diamond is grown according to themethod of the invention sequentially on the 6 {100} faces of thesubstrate. By this method the three-dimensional growth of colorless,single-crystal diamond can produce diamonds about 300 carats in weightand about 1 inch in each dimension.

FIG. 11 is an IR absorption spectrum (2500-8000 cm⁻¹) for a colorlessSC-CVD diamond produced according to the method of the invention, e.g.,with a deposition chamber atmosphere comprising from about 5% to about25% O₂ per unit of CH₄, and a brown SC-CVD diamond produced with N₂ gaspresent as a component of the deposition chamber atmosphere. Thespectrum for the brown SC-CVD diamond produced with N₂ gas had peaks at2931, 3124, 6427, 6857, 7234, and 7358 cm⁻¹. Those peaks are absent inthe spectrum for the colorless diamond produced according to the methodof the invention with O₂ gas present. The data, therefore, show thatthere are no near IR or mid IR impurities due to hydrogen in thecolorless diamond produced according to the method of the invention withO₂ gas present. This further demonstrates that the method of theinvention produces very pure, large single-crystal diamond at a highgrowth rate.

The colorless, single-crystal CVD diamond material may be prepared for arange of industrial and other applications, including, but not limitedto, uses in electronics, optics, and as a colorless gem.

Other aspects of the invention can be understood in greater detail fromthe following examples.

EXAMPLE 1

A diamond growth process was conducted in the above-described MPCVDchamber in FIG. 1. First, a commercial 3.5×3.5×1.6 mm³ high pressurehigh temperature (HPHT) synthetic type Ib diamond seed was positioned inthe deposition chamber. The diamond seed has polished, smooth surfacesthat were ultrasonically cleaned with acetone. The deposition surfacewas within two degrees of the {100} surface of the diamond seed.

Then, the deposition chamber was evacuated to a base pressure of 10⁻³torr. The infrared pyrometer 142 was focused though a quartz window atan incident angle of 65 degrees on the growth surface of the diamond andhad a minimum 2 mm² diameter spot size. Diamond growth was performed at160 torr pressure using gas concentrations of 15% O₂/CH₄, and 12%CH₄/H₂. The process temperature was 1020° C., and gas flow rates were500 sccm H₂, 60 sccm CH₄, and 1.8 sccm O₂. Deposition was allowed tocontinue for 12 hours.

The resulting diamond was 4.2×4.2×2.3 mm³ unpolished, and representedabout 0.7 mm of growth on the seed crystal that was grown at a growthrate 58 microns per hour. The growth morphology indicated that the <100>side growth rate was faster than the <111> corner growth rate. Thegrowth parameter, α, was estimated at 2.5-3.0.

The deposited diamond was characterized using optical microscopy, x-raydiffraction (XRD), Raman spectroscopy, and photoluminescence (PL)spectroscopy. The optical microscopy and X-ray diffraction study of theresulting diamond confirmed that it was a single-crystal.UV-visible/near infrared transmission spectra of the MPCVD grown diamondseparated from the seed diamond is distinct from MPCVD diamond grown inthe presence of N₂ gas and matches pure (Type IIa) diamond.

A number of MPCVD diamonds were produced according to the guidelines ofExample 1 while varying the described process temperature. Theseexperiments demonstrate the process temperature ranges for producingvarious types of diamond in the growth process according embodiments ofthe present invention.

Diamond produced by the above methods and apparatus will be sufficientlylarge, defect free and translucent so as to be useful as, for example,windows in high power laser or synchrotron applications, as anvils inhigh pressure apparatuses, as cutting instruments, as wire dies, ascomponents for electronics (heat sinks, substrates for electronicdevices), or as gems. Other examples of uses or applications for diamondmade by the above methods and apparatus include the following:

-   a.) wear resistant material—including, but not limited to,    water/fluid jet nozzles, cutting instruments (e.g., razors, knives),    surgical instruments (e.g., surgical blades, cutting blades for    surgical instruments), microtone, hardness indentor, graphical    tools, stichels, instruments used in the repair of lithographic    pieces, missile radomes, bearings, including those used in    ultra-high speed machines, diamond-biomolecule devices, microtomes,    and hardness indentors;-   b.) optical parts—including, but not limited to, optical windows,    reflectors, refractors, lenses, gratings, etalons, alpha particle    detectors, and prims;-   c.) electronics—including, but not limited to, microchannel cooling    assemblies; high purity SC-CVD diamonds for semiconductor    components, SC-CVD doped with impurities for semiconductor    components-   d.) anvils in high pressure apparatuses—including, but not limited    to, the “Khvostantsev” or “Paris-Edinburgh” toroid shaped anvils    that can be used with multiple optical, electrical, magnetic, and    acoustic sensors; Bridgman anvils that are relatively large, have    variable heights, and include major angles [15]; Multianviles,    Drickamer cells, belt apparatus, piston-cylinder apparatus;    precompressing samples for laser or magnetic shock wave studies;    colorless, smooth coating for hydrogen and other applications,    apparatus for pre-compressing samples for lasers or magnetic shock;-   e.) containers—including, but not limited to, 6 edge {100} plated    diamonds can be connected to each other to form a container, CVD    diamond coating can be further employed to form a vacuum tight    container;-   f) laser source—including, but not limited to, annealing SC-CVD    diamond to form a stable H3 center (nitrogen aggregate, N-V center,    Si center, or other dopants;-   g.) superconductor and conducting diamond—including, but not limited    to, HPHT annealing with SC-CVD diamond grown with an impurity such    as H, Li, N, Mg, or another low atomic weight element with a size    approaching that of carbon;-   h.) substrate for other CVD diamond growth—using CVD plates as    substrates for CVD growth has the advantage over natural or HPT    substrates in large size and toughness (to avoid cracking during    growth).

In one embodiment, the present invention is directed to anvils in highpressure apparatuses, wherein the anvils comprise CVD diamond,preferably single-crystal CVD diamond. Anvils comprising single-crystalCVD diamond can be used at higher pressures than anvils made of othermaterials, such as tungsten carbide. Anvils comprising single-crystalCVD diamond, moreover, are also beneficial in facilitating more andbetter test results, since the diamond is transparent to neutron, x-ray,and other electromagnetic radiation. Examples of anvil designs that cancomprise single crystal CVD diamonds include Bridgman anvils, including,but not limited to, Bridgman anvils that are relatively large, includevariable heights, and include major angles and Paris-Edinburgh toroidanvils, including, but not limited to, those discussed in [15].

In another embodiment, the present invention is directed to asingle-crystal CVD diamond that is laser inscribed with identifyingmarks (e.g., name, date, number) and a method of preparing such adiamond. The identifying marks, which can take the form of, e.g., lines,text, figures, or symbols, can be laser inscribed onto a diamondsubstrate prior to starting the CVD process to prepare a single-crystaldiamond. The mark is transferred to the single-crystal diamond throughthis process.

Laser inscription of single crystal diamond can have many applications,including, but not limited to, diamond certification and provenance.Laser inscription can also be used to create “designer” gems, i.e.,individualized gems with embedded, customer-requested marks such as textor symbols. The marks inscribed into the diamond cannot be polished off,in part because they can be embedded deep into the diamond.

Other applications of the laser inscription technology can includeproducing embedded circuits and electrical contacts in which laserinscription is used to create a “graphitized” and electricallyconductive path in the diamond. Such localized laser cutting can also beuseful for removing unwanted regions of poorly crystallized CVD diamondduring the synthesis stage (e.g., in much the same way that a dentistwould clean out a cavity in a tooth). This latter application can beparticularly important during the long synthesis of a very large diamondthat may develop problematic growth regions. The applicants have alreadyperformed successful work in this area.

A variety of lasers can be used to perform laser inscription, including,but not limited to, ultraviolet (e.g., excimer) lasers, infrared lasers,high power visible lasers or focused x-ray lasers. In preferredembodiments of the invention, a near-infrared (Nd-YAG) laser built byBettonville N V of Belgium was used to inscribe marks into singlecrystal diamond.

Another embodiment, which is a variation of the above describedapplications, is the use of focused ion or electron beams. Ions can beimplanted to change the conducting properties and introduce specificdefects near a diamond surface. For example, one area of great interestis introducing nitrogen defects for quantum computing. The above methodscan be used to create regions of unique chemistry in single crystaldiamond by “writing” with specific elements (e.g., selective ionimplantation) or with electron beams (e.g., controlled defectpatterning) within a wafer or block using subsequent overgrowth ofdiamond.

The colors of diamond formed by the methods discussed above can bechanged by annealing. For example, a yellow or brown diamond can beannealed into a green diamond.

Single-crystal CVD diamonds of other colors can also be prepared.

Examples of such diamonds used in anvils include the following

-   1.) mixed red, green, and blue CVD layers inside the anvil to    produce a white color;-   2.) coating a thin CVD boron layer on the table to make a vivid blue    color; and-   3.) using a partial blue and green CVD with a yellow seed to produce    a rainbow effect.

FIG. 12 shows a cross-sectional view of a water jet cutter. The jewelholds back high pressure (e.g., about 55,000 psi) water to form a highvelocity water jet. This jet of water then enters a venturi whereabrasive is introduced. The mixture of abrasive, water, and air, thenmixes in the mixing tube to form a jet capable of cutting steel or justabout any other material. Not unexpectedly, the jewel and the mixingtube are placed under an enormous amount of pressure and are thussubject to rapid wear. This is especially true of the mixing tube, dueto the presence of the abrasive. In one embodiment, the mixing tube andjewel comprise single-crystal CVD diamond produced by methods previouslydescribed. In another embodiment, other components of the water jetcomprise single-crystal CVD diamond.

FIG. 13 shows a cubic container configuration comprising single-crystalCVD diamond. Such a container can be produced, for example, by coatingthree separate six {100} face plates with CVD diamond using theaforementioned CVD techniques. The face plates prior to coating can beCVD diamonds, single-crystal CVD diamonds, HPHT diamonds, or naturaldiamonds. These face plates essentially act as seeds on which CVDdiamond is coated. The smaller area, thin plates can then be placed ontop of a larger area, thicker plate, which contains a substantiallysquare hole created by a laser. The entire assembly can then be placedback into the deposition chamber where an additional CVD diamond coatingalong all {100} faces will seal the pieces together.

FIG. 14 shows another container design in which CVD diamond is grown ontwo plates placed together in a step configuration. The end result is tocreate a larger plate through the step-like mosaic fusion of smallerplates. The plates will fuse well together on the top surfaces if all ofthe plates possess 3 {100} faces and are aligned in the same direction(i.e., have an alignment within 10 degrees of each other). The largerplate created using this method can be used as, for example, a seed forfurther CVD diamond growth.

FIG. 15 a) shows a diamond anvil cell and gasket supported with abinding ring.

FIG. 15 b) shows a beveled diamond anvil. The thick lines show the shapeof an anvil surface that would be machined to maximize performance. Thisis the Toroid-type design previously made of tungsten carbide.

As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims, and therefore allchanges and modifications that fall within the metes and bounds of theclaims, or equivalence of such metes and bounds are therefore intendedto be embraced by the appended claims.

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1. A process for producing a laser inscribed mark on a single crystalCVD diamond, the process comprising: i) laser inscribing a mark onto adiamond substrate prior to initiating the CVD process to prepare asingle-crystal diamond; ii) controlling the temperature of a growthsurface of the diamond such that the temperature of the growing diamondcrystals is in the range of 900-1400° C. and the diamond is mounted in aheat sink holder made of a material that has a high melting point andhigh thermal conductivity to minimize temperature gradients across thegrowth surface of the diamond; and iii) growing single-crystal diamondby microwave plasma chemical vapor deposition on the growth surface of adiamond in a deposition chamber having an atmosphere greater than 150torr, wherein the atmosphere comprises from about 8% to in excess ofabout 30% CH₄ per unit of H₂, wherein the mark is transferred from thediamond substrate to the single crystal CVD diamond through thisprocess.
 2. The process of claim 1 further comprising using from about 5to about 25% O₂ per unit of CH₄ in the deposition chamber atmosphere.